The present invention relates to protective materials and more particularly to anti-ballistic ceramic articles and inserts.
Personal ballistic body armor, particularly vests, helmets, and other anti-ballistic articles, are formed generally of anti-ballistic materials which serve to prevent penetration of a bullet. These articles and vests are primarily used for the armed forces but have police and civilian applications as well. However, most are unable to protect properly against trauma, and many are unable to protect against armor piercing bullets. In order to increase the protection provided by conventional body armor, anti-ballistic inserts are incorporated into existing personal ballistic vests. These inserts generally include a ceramic plate for insertion into a pocket in the vest.
However, these inserts must protect against bullet threats as exhibited from armed forces weaponry rifles and the bullets used in such rifles, including armor piercing (AP). The higher bullet threats are of the armor piercing variety, which are stopped by ceramic inserts or other ceramic articles.
In order to stop, i.e., prevent penetration of an AP ballistic threat at a reasonable weight, it has been found that a composite ceramic base must be applied in the form of a ceramic insert in the vest. The least expensive and simplest way is to apply a monolithic plate. These plates are tested to one (1) bullet hit in accordance with the National Institute of Justice NIJ standard 0101.03 Level IV, as well as other standards. This NIJ standard requires only one (1) shot per sample. When these plates are shot more than once, the probability of penetration is high. This is due to the fact that, when the insert is monolithic, a single bullet will crack the whole insert allowing for penetration upon the second bullet strike.
Alternative monolithic plates can be formed from fibers coated with an elastomer, such as that shown in U.S. Pat. No. 4,613,535.
If a multi-hit ballistic panel is required, i.e., one which can withstand more than one hit, it cannot be attained using monolithic inserts. For this purpose, the insert is made of separate tiles connected together, as by gluing onto a substrate. A bullet hitting the target will destroy one or more tiles at a time, and the remaining tiles serve to prevent penetration along the remainder of the insert. Such inserts are shown, for example, in Israel Patent 120854, EP 488465, and U.S. Pat. No. 4,868,040. These inserts are generally expensive to manufacture, since each tile must be abraded to the correct size and fit on the insert. In addition, the tile connection lines and junctions are weakened points from a ballistic point of view.
U.S. Pat. No. 4,760,611 discloses a bullet-proof waistcoat consisting of a plurality of square plates linked together by hinged joints. Each plate has a ceramic core enclosed in a resilient metal, i.e., an aluminum alloy.
According to the present invention, there is provided a method to produce multi-hit articles based on a monolithic ceramic plate, and the articles formed by the method. Multi-hit articles include those capable of withstanding more than two hits at a distance between hits of between 20 and 100 mm. The invention claims that, in order for a monolithic ceramic article to possess multi-hit capabilities, these ceramics must be arrested. As used in this application, the term arrested means that the ceramic is imprisoned inside an envelope formed of composite materials which press against the ceramic uniformly all over its outer surface. In order to produce such an arrested ceramic, a suitable composition of ballistic materials is provided as a backing for the ceramic, an outer cover, including antiballistic fabric and associated resin, is placed around the backed ceramic, and the product is inserted into an autoclave, hydroclave or other isostatic press, or any similar apparatus or shrink material. Under pressure, the resin is cured, whereby the compression stresses and bonding mechanism serve to xe2x80x9carrestxe2x80x9d the part after the external pressure is released.
There is thus provided in accordance with the present invention, an antiballistic article including a ceramic monolith, an antiballistic backing material affixed to the ceramic monolith, and an outer shell, formed of an antiballistic material including a curable resin, enclosing the backing and ceramic monolith, the curable resin being cured after and while the enclosed backing and ceramic monolith is maintained under isostatic pressure of at least about 10 atmospheres.
There is also provided in accordance with the present invention a method of forming an antiballistic article including the steps of forming a ceramic monolith, affixing an antiballistic backing material to the ceramic monolith, enclosing the backing and ceramic monolith by an outer shell formed of an antiballistic material including a curable resin, placing the enclosed backing and ceramic monolith under isostatic pressure of at least about 10 atmospheres, and curing the curable resin while the enclosed backing and ceramic monolith is maintained under isostatic pressure of at least about 10 atmospheres.